The goal is to remain the King of the hill. You become King of the hill by rolling higher on a d100 than the current King.
There are a couple of rules and twists to make the game less stale and boring at higher rolls:

• In the event of a tie, the challenger wins
• The numbers 7 and 77 always win as a challenger, but always loses as a king
• The numbers from and including 90 to and including 99 always loses to prime numbers. The exception is 97 (which is a prime number). 97 loses to any multiple of 5.
  These number also lose to any number lower than 10
• The numbers from and including 80 to and including 89 always loses to numbers ending in the same digit as themselves. 7 and 77 is excluded from this rule.
  Examples: 83 loses to 3, 13, 23, 33, etc. and 86 loses to 6, 26, 36, etc.
• When challenging a King with the number 50, flip a coin. Heads, you win; Tails you lose.

• A 1 is a critical failure so bad it affects the current King. The King wins the challenge, but the challenger gets to roll a new number the King must now use.
• A 100 is a critical success. You automatically win, but must roll a new number to use as the King. If you roll another 100 your roll automatically becomes a 60.

Critical rolls and the rule of tie supersedes the other rules.
If you are dethroned you must wait for at least 3 people to challenge new King(s) before you can challenge the current one again.

Obviously this game has a lot of room for cheating and lies, but hopefully you guys can play nice.

I'll selfishly start of as the King with
42

I'll face you, King!

53

Rules update: The rule to wait for 3 people has been reduced to a wait for 2 people to attempt before you can try again.

63

You fool!

97

44

Oops, I didn’t read the 3 people must roll before you can roll again rule. I lost anyway.

Oh I did the same, but until more people get active I don't mind the oversight. Unless you demand your throne back, of course. New King says NAY!

28

I'm already seeing it's going to be a good idea to mention the King's value in your post. Maybe even the name?

So:

Current King:
Mat_Yuren - 86

(also I beat a mod, dare any challenger really take me on?)

Your 86 is no match for my... 94?

Hoping for a prime number... 70

Current King:
JacesAcolyte - 94

77

Edit: Reclaiming my throne! For a brief moment...

Current King:
Mat_Yuren - 77

You fool, nothing can stop me now! 94

Oh, I just reread the bit about 3 challengers, whoops.

Jumping back in here real quick, feel free to challenge more often as long as there are few players.

With that being said, 
Current King:
Mat_Yuren

I challenge you with a 86!

Current king:
Hypathia

I challenge you with a 96!

Current king: DrustriannaMithdetaryl

Your powers are weak, old one. 97!

EDIT: HAHAHAHAHAHAHA

Ah, but you have left yourself open, JacesAcolyte!

94

Edit: Unfortunately I slam really hard into the wall next to the open door! (What's with all the 90 plusses?)

Current kind: JacesAcolyte

Can I get the fourth 90+ in a row? 31

Nope! But yay, prime number!

Current King: DrustriannaMithdetaryl

58

Ah ah ah, not so fast there, Drustrianna:

• The numbers from and including 90 to and including 99 always loses to prime numbers. The exception is 97 (which is a prime number). 97 loses to any multiple of 5.

I am still the king!

EDIT: I hadn't refreshed the page, so I did not see TheGreatOne's 45. Drat.